BowtieBoyAV

Hi,
I have two related questions actually.

Background first: I am checking valvetrain geometry b/c the block has been decked (.005") and heads (Dart LS1 205s) have also been shaved (~.020"). I am helping a friend and I'm affraid his old pushrod length is no longer appropriate. Roller rocker arms are non adjustable Harland Sharp 1.8 ratio. LS7 lifters. Heads came back from the machine shop with installed height of 1.74. GM MLS gasket. It also says "C.B. 1.060"...not sure what that means?

Question 1) I installed the timing gears with the dots lined up, but when I was checking the valvetrain geometry I noticed that the dots were lining up at TDC of intake (the intake valve was starting to open) instead of TDC of compression (the way I thought it would be). Is it correct the way I currently have it or was I 1 whole crank revolution off?

Question 2) The Harland Sharp rocker installation instructions call out ~3/4-1.25 turns after zero lash to achieve the proper preload/torque spec of 22ft-lbs. I know to target a centered wipe pad on the top of the valve stem. To check that geometry I installed a couple lifters I had welded solid to prevent them from collapsing under the valve spring load and giving me false readings.
However, since under normal operation the lifters are actually preloaded, what is the best way to check this and ensure accurate readings? For the sake of checking geometry and determining the proper pushrod length, should I just neglect the lifter preload issue and continue to use the welded lifters?

Thanks very much in advance!

BowtieBoyAV

bump. Anyone?

A.R. Shale Targa

iTrader: (2)

On question #1...when cylinders 1 and 6 are @tdc, one is ready to fire and
the other is setting the ex. valve down and lifting the in. valve (overlap)
Dots on chain both @ 12 o'clock is # 1 and dots together (cam @ 6 o'clock,
and crank @ 12 ) is # 6 ready to pop.
On Q #2 I'm not entirely sure what you're looking for (swipe pattern only ???)
Cuz you need a normal lifter to establish proper p-rod length and lifter
preload ( about .080 ) There's a sticky on here about using the adj. rod

BowtieBoyAV

OK thanks, that is what I was looking for. It struck me as odd that in the service manual's reference condition with the cam dot at 6 o'clock and crank dot at 12, cyl #1 would be at the overlap condition instead of TDC compression.

I'm trying to establish both wipe pattern and pushrod length. I revised my search wording and found some other good posts under the GenIII Internal section. I read through a lot of various discussions. In summary, I think the best one for establishing correct rocker height (i.e. wipe pattern) on a nonadjustable rocker is here. http://forums.corvetteforum.com/1563994999-post1.html


Finally, I think I have most of my questions answered, but just to confirm...
1) Since I dont have light pressure "checker springs" I am correct to determine the rocker height with the solid lifter at zero lash. I just need to figure out my correct shim height to get the ideal wipe pattern.
2) After #1 is determined, I need to add my desired lifter preload to the pushrod length that nets me zero lash with my new rocker height.
3) The spec for LS7 lifter preload is ~.070-.080" ? Just out of curiosity, is that value listed in a GM spec table somewhere or is that just a number based on general experiences?

Thanks again

FWIW: I also compiled these links from my various findings when I revised my search criteria. Hope this can maybe help others in the future.

Then this is helpful for determining pushrod length
https://ls1tech.com/forums/14434320-post3.html

This is another good discussion about calculating proper pushrod length when considering rocker ratio geometry, measurement method, etc.
vettenuts and hiltsy855 have some good calculation and picture examples later on in the post.
https://ls1tech.com/forums/generatio...questions.html

vettenuts

iTrader: (4)

PM Sent

1) The only issue here is that the adjustable pushrod needs to be used with the solid lifter to ensure you are at zero lash. Using it with the valve springs will cause the threads to load up in the adjuster and possibly bend, etc. which may cause some false readings. Not sure if it will damage the adjustable pushrod.

Do you have the tool to swap in check springs? You can buy any light spring that will fit at a hardware store.

2) Correct

3) Do a search on Corvetteforum for posts by "Eric D" who works for GM, I seem to recall he had provided a table of preload values based on GM part number.

BowtieBoyAV

PM sent.

Thanks for the feedback and tips. I guess I better go for the checker springs then. I have some, just never used them. Ill need to pick up a dial indicator as well. I have a little screw type valve spring compressor but it sucks. Last time I tried to use it it kept wanting to tilt over and slip off the top retainer...almost lost a Ti retainer and a pair of valve locks in the process. Since the heads came back from the machine shop with valves and springs assembled, I was trying to avoid messing with it, but it looks like I need to deal with it. These springs exert 360lbs at max lift, plus you factor that back through a 1.8 rocker ratio...hope the adjustable pushrod isnt bent already. Shouldnt be since I didnt get crazy extending it to min thread engagement or anything like that, plus it is a Comp unit which I think is chromoly like their other pushrods, so hopefully it is still good.

Keep ya posted on my progress.

Sales2@Texas-speed

iTrader: (5)

I believe that's the one you're referring to!

Jon@HKE

In case you haven't figured it out yet the 'C/B 1.060' is most likely the coil bind height of the valve springs. Which limits you to about .610" valve lift at that installed height. You may want to verify your valve lift with those 1.8 rockers because you may already be in a coil bind situation.

If you already realized this please disregard